The present invention relates to novel, improved wood preservative formulations and to methods of employing those formulations.
Wood is the building material of choice in a vast variety of applications. This material is subject to relatively rapid deterioration when wet or moist; and wood exposed to the elements is commonly treated to retard deterioration.
The preservation procedures heretofore proposed vary. Typically, a wood preservative such as a chromated copper arsenate (CCA) is mixed with a liquid carrier such as water, and the mixture is introduced under pressure into the wood. In some cases, this is followed by pressure impregnation of the wood with a wax-surfactant-water emulsion. This is commonly known in the industry as a xe2x80x9ctwo-step procedurexe2x80x9d.
These prior art, techniques proved to be ineffective in preserving western wood species such as hemlock against deterioration; and two-step processes are time consuming, require a capital expenditure for additional equipment, have increased operating costs, and are correspondingly expensive. Also, surfactants commonly employed in heretofore proposed wood preservative formulations cause pump and valve seals to rapidly deteriorate.
Another disadvantage common to heretofore proposed wood preservative formulations is that wax-surfactant particles and preservative particles in those formulations are oppositely charged and tend to be attracted to each other. This results in the formation of surfactant-wax-preservative agglomerates which fall out of suspension and form a sludge on the bottom of the treatment tank. This removal of preservative and wax from the preservative formulation makes it ineffective.
There have now been invented, and disclosed herein, certain methods for preserving wood which do not have the drawbacks of those heretofore proposed.
The wood preservative techniques of the present invention involve the pressure impregnation of wood with a single formulation which combines a wood preservative with a wax-surfactant-water emulsion. The wax is employed to control the rate at which the treated wood dries and for water repellency. The surfactant component of the emulsion: (1) makes the preservative-emulsion formulation stable, and (2) promotes penetration of the preservative and wax into the wood being treated.
Treatment of wood in accord with the principles of the present invention is effective in the case of both eastern and western species. The treatment process is both cost and time effective because only a single step and the equipment needed for one step is required and because the ingredients of the preservative formulation do not degrade pump and valve seal materials. The formulation is stable over extended periods of time, is capable of effectively penetrating the wood being treated, and does not foam to an excessive extent when applied under pressure to the wood being treated (a common disadvantage of heretofore proposed wood preservative formulations). Both the wood preservative and the water repellant wax are efficiently introduced into the wood being treated; and the treated wood is not slippery, an important safety feature for decking and other wood that is walked on.
Another important advantage of the present invention mentioned briefly above, is that the wax in the wood preservative formulation acts as a water evaporation retardant. The treated wood therefore dries more slowly than it would if otherwise treated and is less likely to warp, crack, or check. This results in a superior treated product.
The important features, advantages, and objects of the present invention will be apparent to the reader from the foregoing and the appended claims taken in conjunction with the accompanying detailed description and discussion of the invention.